From fea6ac554d9dea849e2517284b17f99fb9be423a Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Google)" Date: Fri, 15 Jul 2022 17:55:55 -0400 Subject: tracing: Add example and documentation for new __vstring() macro Update the sample trace events to include an example that uses the new __vstring() helpers for TRACE_EVENTS. Link: https://lkml.kernel.org/r/20220715175555.16375a3b@gandalf.local.home Signed-off-by: Steven Rostedt (Google) --- samples/trace_events/trace-events-sample.c | 14 +++++++++++-- samples/trace_events/trace-events-sample.h | 32 ++++++++++++++++++++++++++---- 2 files changed, 40 insertions(+), 6 deletions(-) (limited to 'samples/trace_events') diff --git a/samples/trace_events/trace-events-sample.c b/samples/trace_events/trace-events-sample.c index 4d34dc0b0fee..608c4ae3b08a 100644 --- a/samples/trace_events/trace-events-sample.c +++ b/samples/trace_events/trace-events-sample.c @@ -19,9 +19,10 @@ static const char *random_strings[] = { "One ring to rule them all" }; -static void simple_thread_func(int cnt) +static void do_simple_thread_func(int cnt, const char *fmt, ...) { unsigned long bitmask[1] = {0xdeadbeefUL}; + va_list va; int array[6]; int len = cnt % 5; int i; @@ -33,9 +34,13 @@ static void simple_thread_func(int cnt) array[i] = i + 1; array[i] = 0; + va_start(va, fmt); + /* Silly tracepoints */ trace_foo_bar("hello", cnt, array, random_strings[len], - current->cpus_ptr); + current->cpus_ptr, fmt, &va); + + va_end(va); trace_foo_with_template_simple("HELLO", cnt); @@ -48,6 +53,11 @@ static void simple_thread_func(int cnt) trace_foo_rel_loc("Hello __rel_loc", cnt, bitmask); } +static void simple_thread_func(int cnt) +{ + do_simple_thread_func(cnt, "iter=%d", cnt); +} + static int simple_thread(void *arg) { int cnt = 0; diff --git a/samples/trace_events/trace-events-sample.h b/samples/trace_events/trace-events-sample.h index cbbbb83beced..1a92226202fc 100644 --- a/samples/trace_events/trace-events-sample.h +++ b/samples/trace_events/trace-events-sample.h @@ -141,6 +141,27 @@ * In most cases, the __assign_str() macro will take the same * parameters as the __string() macro had to declare the string. * + * __vstring: This is similar to __string() but instead of taking a + * dynamic length, it takes a variable list va_list 'va' variable. + * Some event callers already have a message from parameters saved + * in a va_list. Passing in the format and the va_list variable + * will save just enough on the ring buffer for that string. + * Note, the va variable used is a pointer to a va_list, not + * to the va_list directly. + * + * (va_list *va) + * + * __vstring(foo, fmt, va) is similar to: vsnprintf(foo, fmt, va) + * + * To assign the string, use the helper macro __assign_vstr(). + * + * __assign_vstr(foo, fmt, va); + * + * In most cases, the __assign_vstr() macro will take the same + * parameters as the __vstring() macro had to declare the string. + * Use __get_str() to retrieve the __vstring() just like it would for + * __string(). + * * __string_len: This is a helper to a __dynamic_array, but it understands * that the array has characters in it, and with the combined * use of __assign_str_len(), it will allocate 'len' + 1 bytes @@ -256,9 +277,10 @@ TRACE_DEFINE_ENUM(TRACE_SAMPLE_ZOO); TRACE_EVENT(foo_bar, TP_PROTO(const char *foo, int bar, const int *lst, - const char *string, const struct cpumask *mask), + const char *string, const struct cpumask *mask, + const char *fmt, va_list *va), - TP_ARGS(foo, bar, lst, string, mask), + TP_ARGS(foo, bar, lst, string, mask, fmt, va), TP_STRUCT__entry( __array( char, foo, 10 ) @@ -266,6 +288,7 @@ TRACE_EVENT(foo_bar, __dynamic_array(int, list, __length_of(lst)) __string( str, string ) __bitmask( cpus, num_possible_cpus() ) + __vstring( vstr, fmt, va ) ), TP_fast_assign( @@ -274,10 +297,11 @@ TRACE_EVENT(foo_bar, memcpy(__get_dynamic_array(list), lst, __length_of(lst) * sizeof(int)); __assign_str(str, string); + __assign_vstr(vstr, fmt, va); __assign_bitmask(cpus, cpumask_bits(mask), num_possible_cpus()); ), - TP_printk("foo %s %d %s %s %s %s (%s)", __entry->foo, __entry->bar, + TP_printk("foo %s %d %s %s %s %s (%s) %s", __entry->foo, __entry->bar, /* * Notice here the use of some helper functions. This includes: @@ -321,7 +345,7 @@ TRACE_EVENT(foo_bar, __print_array(__get_dynamic_array(list), __get_dynamic_array_len(list) / sizeof(int), sizeof(int)), - __get_str(str), __get_bitmask(cpus)) + __get_str(str), __get_bitmask(cpus), __get_str(vstr)) ); /* -- cgit